# Wave Propagation Group Research & Development Activities

## OCEAN SOUND PROPAGATION MODELING

The core of the group's activities is the development of mathematical models that simulate the phenomena of acoustic wave propagation in the sea environment. These models solve boundary value problems in unbounded domains based on the wave equation, the Helmholtz equation, and parabolic approximations of the latter. Special attention is paid for the correct modeling of the sound propagation in the sea bed. The methods and the computer codes developed can be applied in 2 or 3 dimensions, as well as in horizontally stratified or horizontally varying environments relative to the properties of the water column and the bottom. The development of efficient methods for the calculation of broadband acoustic fields and associated time-frequency analysis belong to the activities of the group.

### IACM contributions

- Parabolic approximation
- Non-local boundary conditions (impedance)
- Propagation modelling based on normal/coupled-mode theory
- Broadband propagation / propagation in the time domain
- Sensitivity behavior of underwater acoustic observables
- Time-frequency analysis
- High-frequency asymptotics

### Related Publications

- E.K. Skarsoulis, B.D. Cornuelle, M.A. Dzieciuch, Long-range asymptotic behavior of vertical travel-time sensitivity kernels, Journal of the Acoustical Society of America, in print, 2013.
- E.K. Skarsoulis, B.D. Cornuelle, M.A. Dzieciuch, Second-order sensitivity of acoustic travel times to sound-speed perturbations, Acta Acustica, Vol. 97, pp. 533-543, 2011.
- E.K. Skarsoulis, B.D. Cornuelle, M.A. Dzieciuch, Travel-time sensitivity kernels in long-range propagation, Journal of the Acoustical Society of America, Vol. 126, pp. 2223-2233, 2009.
- G.S. Piperakis, E.K. Skarsoulis, G.N. Makrakis, Rytov approximation of tomographic receptions in weakly range-dependent ocean environments, Journal of the Acoustical Society of America, Vol. 120, pp. 120-134, 2006.
- G.N. Makrakis, E.K. Skarsoulis, Asymptotic approximation of ocean-acoustic pulse propagation in the time domain, Journal of Computational Acoustics, Vol. 12, pp. 197-216, 2004.
- E.K. Skarsoulis B.D. Cornuelle, Travel-time sensitivity kernels in ocean acoustic tomography, Journal of the Acoustical Society of America, Vol. 116, pp. 227-238, 2004.
- G.D. Akrivis, V.A. Dougalis, G. E. Zouraris, Finite difference schemes for the parabolic equation in a variable depth environment with a rigid bottom boundary condition. SIAM J. Numer. Anal. Vol. 39, pp. 539-565, 2001.
- E.K. Skarsoulis, Fast Coupled-Mode Approximation for Broadband Pulse Propagation in a Range-Dependent Ocean,
*IEEE Journal of Oceanic Engineering*., Vol. 24, pp. 172-182, 1999. - G.N. Makrakis, Parabolic approximation of nonlocal boundary conditions in ocean acoustics,
*Applicable Analysis*, Vol. 66, pp. 214-220, 1997. - G.N. Makrakis, Asymtpotic study of the elastic seabed effects in ocean acoustics,
*Applicable Analysis*, Vol. 66, pp. 357-375, 1997. - E.K. Skarsoulis, Second-order Fourier synthesis of broadband acoustic signals using normal modes,
*Journal of Computational Acoustics*, Vol. 5, pp. 355-370, 1997. - V.A. Dougalis and N. A. Kampanis, Finite element methods for the Parabolic Equation with interfaces,
*Journal of Computational Acoustics*, Vol. 4, pp. 55-88, 1996 - V.A. Dougalis, G. D. Akrivis and G. E. Zouraris, Error estimates for finite difference methods for a wide-angle parabolic equation,
*SIAM Journal of Numerical**Analysis*, Vol. 33, pp. 2488-2509, 1996. - J. S. Papadakis and B. Pelloni, Treatment of a sloping bottom with an impedance condition incorporate in the parabolic approximation,
*Journal of Computational Acoustics*, Vol. 4, pp 89-100, 1996 - J. S. Papadakis, Exact non-reflecting boundary conditions of parabolic-type approximations in underwater acoustics,
*Journal of Computational Acoustics*, Vol. 2, pp 83-98, 1996. - J. S. Papadakis, Propagation modeling in Underwater Acoustics: Future Trends,
*Acta**Acustica*, Vol. 82, p. 104, 1996. - M.I. Taroudakis, A Coupled-Mode Formulation for the Solution of the Helmholtz Equation in the Water in the Presence of a Conical Sea-Mount,
*Journal of**Computational Acoustics*, Vol. 4, pp 101-121, 1996. - J.S. Papadakis, M.I. Taroudakis, P.J. Papadakis and B. Mayfield, A New Method for a Realistic Treatment of the Sea Bottom in the Parabolic Approximation,
*Journal of the Acoustical Society of America*, Vol. 92, pp 2030-2038, 1992. - M.I. Taroudakis, G.A. Athanassoulis and J.P. Ioannidis, A Variational Principle for Underwater Acoustic Propagation in a Three-Dimensional Ocean Environment,
*Journal of the Acoustical Society of America*, Vol. 88, pp 1515-1522, 1990.

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